Interpretive Summary: Astronauts are exposed to particles of radiation while on exploratory missions in space. Previous experiments have indicated that exposure to some of these particles can cause disturbances in cognitive performance. These experiments investigated how the physical characteristics of different radiation particles affect cognitive performance in rats by running a battery of tests evaluating ability to respond to environmental stimuli. This study revealed that different radiation particles disrupted cognitive performance as a function of the energy of the specific particle, but not the same within and/or between particles. The findings of this study show potential implications of exposure from space travel.

Technical Abstract:
On exploratory class missions astronauts will be exposed to range of heavy particles which differ in terms of particle energy and particle linear energy transfer. The present experiments were designed to evaluate how these physical characteristics of different particles affect cognitive performance, specifically operant performance. Following exposure to Si28, TI48, C12 and O16 particles at the NASA Space Radiation Laboratory, rats were tested for their ability to respond appropriately to changes in reinforcement schedules using an operant task. The results showed that the effectiveness of different particles in disrupting cognitive performance, defined as the lowest dose that produced a performance decrement, varied as a function of the energy of the specific particle: for comparisons between different energies of the same particle the effectiveness of the particle was directly proportional to particle linear energy transfer, whereas for comparisons between different particles effectiveness is inversely proportional to particle linear energy transfer. The results are discussed in terms of the mechanisms that influence the effectiveness of different particles and energies and in terms of their implications for risk analysis.